Data storage systems are a staple in digital mass storage for back-up and server applications. More specifically they are commonly used to archive data, i.e., stored data that is not immediately needed by a host computer. When a host computer needs the data, a request is sent out to the storage system to retrieve the data.
Within the storage system, data is typically archived on physical long term storage media, such as, tape, magnetic disk, optical disc, solid state memory, for example. When a request is received for data, the storage system identifies the physical long term storage media containing the specified data and a robot transport mechanism is dispatched to retrieve the long term storage media and provide it to a data transfer interface that is capable of establishing a communication path between the storage media and the requesting host computer.
One example of a storage system is a tape cartridge library. Other variations of storage systems utilizing disks, banks of memory chips or other long term storage media are also available.
In a tape cartridge system, as well as most other media storage system, there are typically a plurality of shelves structured to at least removably store a tape cartridge. In some instances, the tape cartridges or other media are themselves stored in movable packs that are themselves removably stored on shelf structures.
The storage system may have more than one drive (data transfer interface) for reading data from and writing data to the storage media. Further, the library may have more than one robot operating within the storage system to transport storage media between the storage shelves and the read/write drives.
As physical movement is an inherent characteristic of such systems, the time involved in responding to a host computer request can be a factor in overall storage system performance.
Shown in FIG. 1 are exemplary prior art storage systems 100 and 102. As illustrated, in many instances such storage systems have been designed such that the distance 104 between any given storage location 106 and the data transfer interface 108 is substantially equal. This is to say that the transport time of data storage media 110 from any given storage location 106 to the data transfer interface 108 is substantially the same. Such substantially equidistant, substantially equal time transfer storage systems are generally either substantially circular 112, or semi-circular 114.
Where multiple levels of storage are involved, either each layer is generally provided with its own data transfer interface 108 such that the transfer time for all locations 106 on all layers is about the same.
Though perhaps beneficial for equalizing transport time, such generally circular systems can be cumbersome to install, especially in pre-existing locations where square or rectangular systems would be preferred for economy of floor space.
It is to innovations related to this subject matter that the claimed invention is generally directed.